ARM: mach-shmobile: Use INTC_IRQ_PINS_16H on sh7372

Use INTC_IRQ_PINS_16H on sh7372 to have two separate
interrupt controllers for the external IRQ pins.

This is preparation work for future IRQ domain support.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>